1. Field of the Invention
The present invention relates generally to electrical connectors, and more particularly to a connector for electrically interconnecting a plurality of terminals of an electronic module to corresponding terminals of a backplane assembly.
2. Discussion of Related Art
Connectors for electrically connecting electronic modules to a backplane assembly typically comprise a connector body of insulative material attached to a backplane surface. These connectors have a slotted opening that runs longitudinally through the center of the connector body with V-shaped contacts positioned within the slotted opening. When a board edge from an electronic module is inserted into the slotted opening in the connector body, interface circuit paths on the board engage with the V-shaped contacts to complete the interface between the module and the backplane.
Backplane connectors for applications requiring a higher contact density comprise two halves of insulative material. One half is attached to a module, while a second mating half is attached to the backplane surface. Individual contacts of conductive material are embedded in the body of each half connector. Typically, the contacts in one connector half are shaped as rectangular blades. The corresponding contacts in the other connector half are then shaped as tuning forks. The transverse axes of the two sets of contacts are arranged 90 degrees apart from each other. In this way, each rectangular blade enters the crotch of a corresponding tuning fork when the two connector halves are forced together. The contacts are dimensioned such that the connection forms a frictional bond that is reliable and gas-tight.
Throughholes are generally used to pass the connector contacts through the backplane. Throughholes are drilled into the module and the backplane in a pattern that aligns with the contact pattern on the connector halves. The non-mating ends of the contacts on each connector half are then inserted in the throughholes. On the backplane, the contacts are secured through a press fit. On the module, contacts are typically attached by soldering, a tedious and labor intensive operation. A polarized pin and key arrangement usually secures each connector half mechanically to the module or the backplane. The contacts may be connected as desired by wire-wrapping the non-mating ends of the contacts. Alternatively, the throughholes may be plated and connections between contacts made by plating circuit paths on the backplane.
Conventional connectors for backplanes have several drawbacks. The contact mating technique for connectors having two halves of insulative material makes module insertion and extraction difficult. When a rectangular blade contact mates with a tuning fork contact, the bond formed is highly frictional. The mated contacts are particularly resistant to axial forces of stress and strain. Individual contact engagement often requires a force of up to 2.25 ounces. For a backplane connector having 396 contacts, the connector mating force may approach 50 pounds. Consequently, the addition or removal of a module from a backplane requires the use of extraction and insertion tools. These tools generally apply a force at the back edge of the module with a lever technique.
The tuning fork and rectangular contacts in conventional backplane connectors are also highly susceptible to misalignment and damage. Exact alignment between each of the several hundred rectangular blades and tuning forks is necessary for the connector halves to match. When repeated making and breaking of the contacts occurs over time, bending of some contacts is likely, which may eventually lead to contact damage. Contact damage renders the module, backplane, or both useless until the damaged contacts are repaired. Even slight misalignment between one pair of corresponding contacts will increase the required insertion and extraction forces. Misalignment can prevent the installation of a module. Repeated engagement can also lead to contact surface corrosion due to the wiping action of the blade in the tuning fork. This corrosion may eventually increase contact resistance.
Moreover, the passing of contacts through the backplane via throughholes limits the contact density in the prior art. Grid spacing for backplane throughholes for a conventional connector is generally limited to 0.10 inches by 0.05 inches. Practical limitations such as the size of the contacts inserted into the throughholes, the need to maintain the structural integrity of the backplane, and the spacing required between throughholes for circuit paths prohibit increasing the contact density for existing designs. The soldering of several hundred contacts to the plated throughholes is also labor intensive and tedious.
In light of the foregoing, there is a need for a backplane connector for interconnecting electronic modules that minimizes the need for insertion and extraction tools, lowers the risk of contact damage, permits a higher interconnect density, comprises fewer assembled parts, and requires less assembly labor.